Thermal insulated intake ports

ABSTRACT

Reduced fuel consumption of spark ignition reciprocating internal combustion engines is achieved by coating the intake port area of the engine with a thermally insulating material.

BACKGROUND OF THE INVENTION

This invention relates to improvements in spark-ignition reciprocatinginternal combustion engines, and more particularly to improvements inthe fuel inlet port area whereby reduced fuel consumption is achieved.

Research efforts concerning internal combustion engines haveconcentrated on problems as they have developed. For example, for theproblem of "rumble" in high compression engines one solution isthermally insulated combustion chambers as described in U.S. Pat. Nos.3,019,277 and 3,066,663 to T. P. Rudy. The use of gasoline detergents tocontrol the adverse effect of intake system deposits from the fuel isdescribed by G. H. Amberg and W. S. Craig in SAE Paper 554D presented atLos Angeles, Calif. In August, 1962. As part of this study the authorsused synthetic deposits prepared from a two part epoxide-curing agentadhesive to study the desired range of deposits. In those rotary pistonengines having both inlet and outlet passages and the bearing for theinner rotary piston located in a single member, the use of protectivelacquer in said passages to reduce heat flow to the bearing is describedin U.S. Pat. No. 3,115,871 to Luck.

Today, the rapid depletion of petroleum supplies in the world coupledwith rapid escalation of costs for gasoline fuel for spark ignitionreciprocating engines, mandates the implementation of all improvementsto conserve precious fuel supplies. The present invention provides arelatively simple, unexpectedly efficient improvement in such engines toimprove their fuel efficiency, particularly at low speeds. Further,there is some evidence that certain coatings according to the inventionmay reduce ultimate octane requirement increase typically experiencedafter mileage accumulations.

SUMMARY OF THE INVENTION

The invention provides a spark ignition reciprocating internalcombustion engine for use with gasoline fuel said engine having anintake port area extending between an intake manifold and an intakevalve, said intake valve disrupting flow of a fuel-air mixture into acombustion chamber of said engine; and having a substantial portion ofthe surface of said intake port area coated with a thermal insulatingmaterial for reducing transfer of heat to the fuel-air mixture whichtraverses said intake port area during operation of the engine; saidthermal insulating material including inorganic and resinous materialshaving in their chemical structure an element selected from fluorine,silicon, and/or sulfur.

The invention further provides a method for reducing the fuelconsumption of a gasoline fueled spark ignition reciprocating enginehaving an intake port area extending between an intake manifold and anintake valve, which comprises coating a substantial portion of thesurface of said intake port area with a thermally insulating materialselected from inorganic materials and synthetic resinous materialshaving in their structure an element selected from fluorine, silicon andsulfur.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a partial horizontal sectional view through an enginecylinder embodying the present invention showing a thermal insulatingcoating on the surface of the inlet port area.

DESCRIPTION OF PREFERRED EMBODIMENTS

It is known that with modern gasolines containing detergent additivesthat it is possible to prevent, or substantially reduce the formation ofcarbonaceous deposits in the fuel inlet systems of spark ignitiongasoline engines. Applicants have unexpectedly discovered that byapplying a controlled thermal insulation as herein defined to the inletport area that reduced fuel consumption can be achieved.

An engine constructed in accordance with this invention is shown in thedrawing and includes a cylinder 10 with a piston 11 and connecting rod12 which runs to a crankshaft, not shown. The top of the cylinder mountsa cylinder head 15 which is provided with an intake port 12 extendingbetween intake manifold 18 and intake valve 19. The surface of theintake port is coated with a thermal insulating material 20, forreducing transfer of heat from the engine to the fuel/air mixture whichtraverses the intake port during operation of the engine.

The insulating coatings of this invention have a thermal conductancefrom about 30 B.T.U./hr./sq ft/°F. to about 5000 B.T.U./hr./sq. ft/°F.For example, a 30 mil coating of polyphenylene sulfide having a thermalconductivity of 2 B.T.U./hr/sq. ft/°F./in. has a thermal conductance ofabout 67 B.T.U./hr/sq. ft/°F. In a preferred embodiment of the inventionthe insulating coating has a thermal conductance from about 50 to about1000 B.T.U./hr/sq. ft/°F.

Any conventional method of applying the thermal insulation to the inletport area can be employed. The insulating material of the invention isan inert coating of low thermal conductivity having high resistance tothermal shock and which may be an inorganic ceramic type of material ora synthetic resinous polymeric material having in its structurefluorine, silicon or sulfur. These coating materials ordinarily will beemployed in thicknesses from about 0.5 to about 75 mils and preferablyfrom about 2 to 70 mils with optimum thickness within this range beingdetermined by engine design and the thermal conductivity of theparticular coating material employed. The coating materials employed inthis invention will have adhesive and cohesive properties adequate toavoid fracturing or peeling during operations of the engine.

Preferably the coating material will also have high melting point, e.g.,above about 450° F., and more preferably above 475° F.; good mechanicalstrength, low coefficient of thermal expansion and low thermalconductivity.

A wide variety of refractory type oxide coatings can be employed. Forexample, the oxides of zirconium, chromium, titanium, cerium andmanganese and certain phosphates, silicates, fluoro silicates andoxyhalides of these materials may be used. Exemplary synthetic resinousmaterials include silicone homopolymers and copolymers,polysiloxane-resin; sulfur containing polymers such as polyphenylenesulfide, and fluoro polymers such as polytetra fluoroethylene andfluorinated ethylene propylene copolymer; and mixtures of thesematerials.

The coatings may be applied by any conventional techniques such as, forexample, flame spraying wherein the coating material is melted in aflame gun and sprayed on the surface to be coated; powder coating, forexample, with an electrostatic powder gun which is particularly suitablefor port areas of intricate geometry, and simple powder coating followedby baking; in some instances manual application of curable resins may beused.

It is preferred to employ coatings which contain surface roughness toenhance turbulence of the fuel-air mixture traversing the inlet portarea to enter the combustion chamber. However, the coating should notimpede flow during high speed operations.

The coating according to the invention will substantially cover allsurfaces within the inlet port area, but not be applied to the valveseat, or to surfaces within the combustion chamber of the engine. It ispreferred that at least 65% and more preferably at least 75% of theinlet port area surface be coated.

The present invention is operative in all spark ignition reciprocatinginternal combustion engines employing gasoline as the major fuelcomponent, including 4 cycle and 2 cycle engines. Furthermore, theconcept of the present invention is equally effective in air cooled andwater-cooled systems. The internal combustion engines having the inletport area coated according to the invention are made of metalsconventionally used in internal combustion engines, i.e., cast iron,aluminum, steel and the like.

It should be understood that an engine according to the presentinvention will ordinarily be operated on a gasoline fuel, i.e., apetroleum fraction boiling in the gasoline range (between about 50° F.and about 450° F.). The gasoline may be free of, or may contain smallamounts, e.g., 0.01-3.17 grams per gallon of organometallic anti-knockcompounds such as tetraethyl lead, tetramethyl lead, methylcyclopentandienyl manganese tricarbonyl, tris(acetyl-acetonate)ironIII,nickel 2-hexylsalicylate and/or vanadium acetyl acetonate and mixturesof these. The invention can be used with commercial gasoline products ofconventional refinery processes such as distillation, thermal cracking,catalytic cracking, alkylation, catalytic reforming, catalyticisomerization and the like. The gasoline fuel may also containconventionally employed additives such as corrosion inhibitors,antioxidants, detergents and up to about 10% by volume of organicmaterials such as methyltertiarybutylether, tertiarybutylacetate,methylalcohol, ethylalcohol and the like.

The following are illustrative examples of the invention showing the useof specific coating compositions according to the invention.

EXAMPLE I

A 1977 model 301 cubic inch (4.9 l) displacement engine installed on adynamometer stand equipped with a flywheel to simulate the inertia of acar was used. The engine had a two barrel carburetor and automatictransmission; standard equipment included exhaust gas recirculation(EGR) and a breakerless electronic ignition system. Specifications ofthe engine included a compression ratio of 8.2, a maximum brakehorsepower of 135 at 4000 rpm and maximum torque of 245 ft-lbs. at 2000rpm. After the engine had been operated for about 2490 hours equivalentto about 90,000 miles of driving operation, the cylinder heads wereunbolted and all accumulated deposits removed from surfaces of theintake ports, intake valves, piston tops and cylinder heads. This workis part of a study detailed in SAE Paper 790938 by L. B. Graiff. Gallyproofs of said paper accompany this application and are incorporatedherein by reference. Fuel consumption was measured at 25, 45 and 65 mph(40, 72 and 105 km/h) equivalent level-road-load speeds by amini-computer, while recording the loss in weight from an electronicbalance of a can of fuel supplying the engine. Readings were recordedevery minute for ten minutes by a computer which also calculated themean and standard deviation. During the fuel consumption tests, theoperating temperatures were maintained as follows: jacket water out, 95°C. (203° F.); oil gallery, 95° C. (203° F.) and carburetor air, 45° C.(113° F.) with a constant humidity (82 grains of water per pound of dryair, or about 20% relative humidity at 45° C). The engine lubricant wasa multigrade 10W40 of API SE Quality. After fuel consumption data on the"clean" (i.e., deposit removed) engine were determined, the head boltswere again removed and substantially all of the intake port surfaceareas in the engine heads were coated with a 15 mil-thick layer ofresinous coating of polyphenylene sulfide resin and a second 15 millayer of a blend of polyphenylene sulfide and polytetrafluoroethyleneresin. The engine was reassembled and the fuel consumption of the enginewas again determined.

                  TABLE I                                                         ______________________________________                                        EFFECT OF AN INTAKE PORT COATING OF                                           POLYPHENYLENE SULFIDE/TFE ON FUEL CONSUMP-                                    TION (1977 Pontiac 301 CID-2V Engine)                                                   Fuel Consumption, g/min                                                       65 mph   45 mph     25 mph                                          ______________________________________                                        Before Coating .sup.a                                                                     182.9      105.6      52.8                                        After Coating.sup.a                                                                       177.1      103.7      52.0                                        % Reduction  3.2        1.8        1.5                                        ______________________________________                                         .sup.a With clean engine, i.e., with no combustion chamber deposits or        port deposits.                                                           

The results as shown in Table I exemplify the beneficial effect on fueleconomy, i.e., lowered fuel consumption according to the invention.Unexpectedly, it was observed that after 375 hours of operation withdetergent-free gasoline the engine having the coated intake portsaccording to the invention, had a lower octane requirement (of about 2octane numbers) than the same engine without the coating for a likeperiod with the same fuel. Visual inspection of the intake port areaafter the 375 hours of operation revealed much smaller accumulation ofhydrocarbonaceous deposits than typically found for this period ofoperation.

EXAMPLE II

A 1977 Ford 351 (M) CID-2V (5.8 l) laboratory engine configured asdescribed in Example I accumulated about 1748 hours of operation atsubstantially the operating conditions described in Example I andsubstantially employing a seven minute cycle consisting of an idle modeand 35 and 65 mph (57 and 105 km/h) cruise modes with attendantaccelerations and decelerations. After fuel consumption was measured atseveral speeds all intake port deposits were removed and fuelconsumption was again determined. After a few hours of operation toensure stable operation, the heads were again removed and the intakeports coated with a curable silicone polymer (G.E. RTV Silicone Sealer)hand applied to an apparent average thickness of about 60 mils. Afterthe silicone had cured at room temperature, the engine was reassembledand fuel consumption determined. The results of this test are shown inTable II.

                                      TABLE II                                    __________________________________________________________________________    EFFECT OF INTAKE PORT DEPOSITS ON FUEL CONSUMPTION                            1977 Ford 351 (M) CID-2V Engine                                               Fuel Consumption                                                              Engine                                                                            65 mph  55 mph  45 mph.sup.a                                                                          35 mph  30 mph                                    Hours                                                                             g/min                                                                             % incr                                                                            g/min                                                                             % incr                                                                            g/min                                                                             % incr                                                                            g/min                                                                             % incr                                                                            g/min                                                                             % incr                                __________________________________________________________________________    1748                                                                              177.6                                                                             --  126.3                                                                             --  92.7                                                                              --  66.5                                                                              --  57.6                                                                              --                                    Removed all intake port deposits                                              1752                                                                              173.0                                                                             -2.6                                                                              123.4                                                                             -2.4                                                                              94.7                                                                              2.0 68.8                                                                               2.3                                                                              61.3                                                                               3.7                                  Coated intake ports with thin layer of G.E. RTV Silicone Sealer               1754                                                                              176.3                                                                              1.9                                                                              125.6                                                                              1.8                                                                              95. 0.4 68.1                                                                              -1.0                                                                              60.0                                                                              -2.2                                  __________________________________________________________________________     .sup.a EGR valve operation erratic at this speed.                        

The data in Table II show reduced fuel consumption at lower speedscompared to the same engine free of the naturally accumulated deposits,but somewhat higher consumption at speeds of 45 mph and above. Theexhaust gas recirculation valve operated erratically at 45 mph and its'effect at this speed is uncertain.

What is claimed is:
 1. In a spark ignition reciprocating internalcombustion engine for use with gasoline fuels said engine having anintake port area extending between an intake manifold and an intakevalve, said valve disrupting flow of a fuel air mixture into acombustion chamber; the improvement which comprises having a substantialportion of the surface of said intake port area coated with a thermalinsulating material for reducing transfer of heat to the fuel/airmixture which traverses said intake port area during operation of saidengine, said insulating material consisting essentially of one of thegroup of polyphenylene sulfide alone and polyphenylene sulfide incombination with synthetic resinous polymeric materials having in theirchemical structure at least one element selected from fluorine andsilicon.
 2. A spark ignition engine as in claim 1 wherein the engine hasa plurality of combustion chambers and a plurality of thermallyinsulated intake port areas.
 3. A spark ignition engine as in claim 1wherein the insulating material has a thermal conductance of from about30 B.T.U./hr/sq.ft/°F. to about 5000 B.T.U./hr/sq.ft/°F.
 4. A sparkignition engine as in claim 1 wherein the insulating material has athermal conductance of from about 50 BTU hr/sq.ft/°F. to about 1000BTU/hr/sq.ft/°F.
 5. A spark ignition engine as in claim 1 wherein theinsulating material which contains fluorine in its chemical structure isselected from polytetrafluoroethylene and fluorinated ethylene propylenecopolymer.
 6. A spark ignition engine as in claim 1 wherein theinsulating material which contains silicon in its chemical structure isselected from silicone homopolymers and copolymers and polysiloxaneresins.
 7. A method for reducing the fuel consumption of gasoline fueledspark ignition engine having an intake port area extending between anintake manifold and an intake valve comprising coating a substantialportion of the surfaces of said intake port area with a thermallyinsulating material consisting essentially of one of the group ofpolyphenylene sulfide alone and polyphenylene sulfide in combinationwith synthetic resinous polymeric materials having in their chemicalstructure at least one element selected from fluorine, and silicon.
 8. Amethod as in claim 7 wherein said insulating material has a thermalconductance from about 30 BTU/hr/sq.ft/° F. to about 5000 BTU/hr/sq.ft/°F.